In recent years, as a light emitting device using an LED element, a chip-on-board (COB) type light emitting device has attracted attention. The chip-on-board technology means a technology where a chip is directly mounted on the circuit pattern of a large package substrate with the chip of a light emitting element etc. not being mounted into a small package once. When a white light emitting device is produced, yellow phosphors are generally included in a sealing resin that seals an LED element after a blue LED element has been mounted.
Here, when the blue LED element is combined with the yellow phosphors, there is a problem that color rendering property is low. Accordingly, when the color rendering property is required for the white light emitting device, a method is adopted where green phosphors and red phosphors are included in the sealing resin in addition to the yellow phosphors. However, in the method where the color rendering property is compensated by various kinds of phosphors when one kind of LED element is used as a light emitting source, loss is large in case that the conversion of wavelength occurs in respective phosphors, which necessarily decreases the amount of light.
The light emitting device described in patent document 1 has been proposed as one which can change color temperature while maintaining high color rendering property, without using red phosphors with particularly large loss. This light emitting device comprises: a device substrate; a light emitting part group of first color temperature and a light emitting part group of second color temperature which are arranged in a predetermined arrangement pattern on the device substrate; a power supply and a circuit pattern which independently supply electric current to each of the light emitting part groups; and a controller which controls the ratio of the electric current supplied to each of the light emitting part groups from the power supply.
Here, the light emitting part group of the first color temperature has a plurality of blue-light-emitting type LED chips and a first phosphor layer which seals these LED chips and includes first phosphors. The light emitting part group of the second color temperature, which is lower than the first color temperature, has LED chips, the first phosphor layer which seals these LED chips, and a second phosphor layer which is arranged on the first phosphor layer and which includes second phosphors.